The present invention relates to brackets for holding a first object with respect to a second object. More particularly, the present invention relates to a side-mount bracket for precisely locating a sensor relative to an object to be sensed. Still more particularly, the present invention relates to a side-mount bracket system, wherein facial interaction between a bracket and a washer results in the washer being fixed positionally with respect to the bracket. The present invention is further related to air gap setting methodologies incorporating abradable setting features, wherein the air gap thereby set is permanently captured at the side-mount bracket system.
Magnetic sensors operate on the principle of detecting magnetic flux density modulation caused by the movement of appropriately configured reluctors (or targets). The magnetic sensor must be affixed very close to the reluctor since its sensitivity decreases very rapidly with the size of the air gap between the reluctor and the magnetic sensor. In most automotive applications, for example, the air gaps are on the order of 0.3 to 1.75 mm. Over such a range of air gaps, the sensor output signal decreases more than ten times. The signal attenuation at large air gaps makes the sensor operation more prone to noise induced failures as well as less accurate in detecting the elements of the reluctor as it spins in relation to the magnetic sensor. Both of these factors are often unacceptable in critical engine control and diagnostic applications.
It may at first glance appear that there would be no problem whatsoever to choose and achieve an appropriate air gap between the magnetic sensor and the reluctor. However, in the majority of production cases, the stack-up of tolerances of the many different components randomly influence the net size of the air gap, which consequently precludes achieving, at each assembly, a precisely predetermined air gap by mere assembly of the parts. As a result, because of the random variations caused by accumulation of tolerances, mere assembly of the parts risks damaging interference between the magnetic sensor and reluctor on the one hand, and inaccurate readings associated with too large an air gap on the other hand. To lessen all the tolerances so that mere assembly assures, at each assembly, the optimum air gap is physically unrealistic and involves inordinate costs associated with manufacturing such precise parts.
The majority of magnetic sensors used in automotive applications involve non-adjustable air gap placement, wherein the stack-up of tolerances causes deviation from the optimal air gap. For example, a rigid bracket is affixed to the body of a magnetic sensor. The magnetic sensor is placed into a sensor port in the engine block, and the bracket is bolted, via a bolt hole in the bracket, to a threaded mounting hole in a mounting surface of the engine block. When the bracket is bolted, the length of the sensor body from the bolt hole of the bracket to the sensor tip determines the air gap with respect to the reluctor, which air gap is affected by the stack-up of tolerances. Even though subject to tolerance related placement inaccuracy, this structural mounting methodology is used widely because of the simplicity of the hardware, and ease of assembly and service.
In situations where air gap variation cannot be tolerated, the air gap is preset during magnetic sensor installation by means of an adjustable bracket, often referred to as a xe2x80x9cside-mountxe2x80x9d bracket. The adjustability of side-mount brackets resides in a bolt slot which allows for the bracket to be adjusted along the slot elongation relative to the threaded mounting hole of the mounting surface.
In one form of operation of the side-mount bracket, the sensor body is placed into the sensor port of the engine block such that the sensor tip is allowed to touch the surface of the reluctor, and then it is withdrawn a distance equal to the predetermined optimum air gap. This method is more time consuming and is error prone.
In another form of operation of the side-mount bracket, a gauging layer of soft, abradable material is placed onto the sensor tip, wherein the thickness of the gauging layer is equal to the optimum air gap. The gauging layer may be either attached to the sensor body or be a part thereof, such as a protuberance, provided the sensor body is of a soft material. Now, the installer need merely place the sensor body into the sensor port until the gauging layer touches the reluctor, and then tighten the bolt on the mounting surface to thereby hold the sensor body at this position. During initial rotation of the reluctor, a portion of the gauging layer is sacrificial to abrasion due to reluctor run-out or differential thermal expansion without damage being incurred to the sensor body or the reluctor.
However, in the event the magnetic sensor must be re-installed, the abraded gauging layer cannot again provide position location for the sensor tip, as it was formerly able to do when it was unabraded. Therefore, before dismounting the magnetic sensor, the bracket must be marked to indicate the correct position of the bolt in the slot of the bracket so that when the xe2x80x9coldxe2x80x9d (original) magnetic sensor is re-installed, the original position of the bolt in the slot can be alignably sightedxe2x80x94not an exact procedure. Indeed, rather than try to reinstall the old, but still usable, sensor using the sighting method to reset the air gap, a technician would rather install a new sensor having the abradable layer intact, thereby circumventing the error prone sighting step otherwise needed to reinstall the old, but usable, sensor. This results in waste of otherwise good sensors and unnecessary expense for the customer or warranty provider. Accordingly, what remains needed in the art, is some way to eliminate the inherently error prone installation procedure of the sighting method, and enable precise and reliable resetting of the air gap during reinstallation of old, but still usable, sensors.
The present invention is a side-mount bracket system for locking the sensor position with respect to a side-mount bracket once the air gap is first established by the gauging layer method, wherein the sensor may be removed and then reinstalled without use of any position setting procedure, yet the air gap is automatically precisely reset to its original value.
The side-mount bracket system according to the present invention includes a washer and a side-mount bracket having an elongated slot, wherein as the washer is brought into the slot, facial interaction therebetween causes the washer to be positionally fixed with respect to the bracket. In this regard, either the slot sidewalls or the washer sidewalls are provided with teeth, the other of the sidewalls are smooth. The teeth are oriented parallel to the direction of insertion of the washer into the slot, referred to herein as the xe2x80x9ctransverse axisxe2x80x9d. The member having the toothed sidewalls is formed of a material harder than the member having the smooth sidewalls. The teeth of the toothed sidewalls may be provided in any suitable form, such as for example serrations, cutting ridges or cutting surfaces. A slight draft is preferred to be provided on the washer sidewalls to facilitate an initial engagement surface of the washer to be inserted into the slot with minimum interference by the slot sidewalls.
The washer and slot are dimensioned so that the sidewalls of the washer tightly abut the sidewalls of the slot, wherein the teeth of the toothed sidewalls inscribe corresponding grooves into the smooth sidewalls as the washer is pressed into the slot along the transverse axis. Consequently, as the corresponding grooves are inscribed, the washer sidewalls are caused to become positionally fixed with respect to the bracket along a xe2x80x9clongitudinal axisxe2x80x9d that is perpendicular to the transverse axis.
Operationally, a sensor body having a sensor tip provided with a gauging layer is placed into a sensor port of an engine block so that the gauging layer comes to rest upon a surface of a reluctor. The gauging layer thereupon immediately establishes the optimum air gap between the sensor and the reluctor along the longitudinal axis. A washer having a bolt hole sized to just fit a preselected bolt is slipped onto the bolt. With a side-mount bracket having an elongated slot preconnected with the sensor, the bolt carrying the washer is passed through the slot and threadably into a threaded mounting hole of the vertical surface. The washer and the slot have complementary sidewalls, wherein one is toothed, the other is smooth, such that the fit therebetween is interfering, wherein the toothed sidewalls score into the smooth sidewalls. Accordingly, as the bolt is tightened, the washer moves along the transverse axis, and facial interaction between the toothed and smooth sidewalls causes the washer to become fixed to the bracket, wherein the position of the sensor is fixed along the longitudinal axis.
During engine operation, a portion of the gauging layer is sacrificially lost to abrasion. However, should the sensor need to be removed and then again replaced, the washer remains fixed to the bracket, and all the installer need do is place the bolt through the mounting hole of the sensor body, through the bolt hole of the washer, and then threadably engage it into the threaded mounting hole of the vertical surface, and the preset air gap will be precisely re-established.
In a second embodiment, the washer may be slidably trapped onto the bracket at the slot, and a tapered bolt having a varying cross-section which causes expansion of the washer as it is threaded home, thereby affixing the washer positionally with respect to the bracket.
In a third embodiment, as a bolt is threaded tightly, annular flanges at either end of a washer are caused to be squeezed onto the bracket adjacent the slot, thereby affixing the washer positionally with respect to the bracket.
Accordingly, it is an object of the present invention to provide a side-mount bracket system which affixes a washer to a side-mount bracket at a positional location indicative of a preset air gap of a sensor attached to the bracket.
It is a further object of the present invention to provide a side-mount bracket system, wherein a predetermined facial interaction between the sidewalls of a slot of a side-mount bracket and the sidewalls of a washer capture a positional location of a sensor with respect to the bracket which is precisely reproducible.
It is another object of the present invention to provide a side-mount bracket system which operates in concert with a gauging layer air gap positioning methodology which retains the air gap setting whether or not any of the gauging layer is sacrificially abraded during operation.
These, and additional objects, advantages, features and benefits of the present invention will become apparent from the following specification.